1. Field of the Invention
The present invention relates to an ozone storage system and an ozone storing method for generating or producing ozone gas by making use of electric energy and storing the ozone gas for supplying it to an ozone consumer continuously at a given flow rate, as it is demanded.
2. Description of Related Art
For having better understanding of the invention, technical background thereof will first be reviewed in some detail. FIG. 28 is a schematic diagram showing generally a system configuration of a conventional intermittent-operation type ozone supply system which is known heretofore and disclosed, for example, in Japanese Unexamined Patent Application Publication No. 3595/1977 (JP-A-52-3595) and which is a typical one of the conventional ozone storage systems. The ozone storage system now of concern is primarily designed for storage of ozone. Referring to the figure, an oxygen containing gas fed from an oxygen supplying source 2 undergoes ozonization under the action of electric discharge within an ozone generator (which is also referred to as the ozonizer) 1. To this end, a circulating blower 3 is provided for feeding the oxygen containing gas supplied from the oxygen supplying source 2 to the ozone generator 1 by way of a circulating pipe L1 as well as for feeding the ozonized oxygen gas as generated to an adsorption/desorption tower 4 for the storage of the ozonized oxygen gas therein.
The ozone storage system further includes a coolant supply source 5 implemented in the form of a refrigerator for generating a refrigerating gas circulated to the adsorption/desorption tower 4 by way of a circulating pipe L2, a heating medium source 6 for generating a heating medium to be circulated to and through the adsorption/desorption tower 4 by way of a circulating pipe L3, and a water ejector 7. The water ejector 7 is so arranged as to extract (desorb) ozone gas under depressurization from the ozonized oxygen gas stored or reserved temporarily within the adsorption/desorption tower 4. Ozone as extracted is then dispersed in water serving as ozone carrier. Thus, ozone can be supplied to the ozone consumer (not shown) in the form of ozone containing water.
Furthermore, in the ozone storage system, there are installed in the circulating pipe L2 change-over valves 8-1 and 8-2 at locations upstream and downstream of the coolant supply source 5, respectively. Additionally, a change-over valve 8-3 is installed in the circulating pipe L1 between a discharge port of the adsorption/desorption tower 4 and a suction or inlet side of the circulating blower 3, while a change-over valve 8-4 is mounted in the pipe L1 between a discharge port of the ozone generator 1 and a suction or inlet port of the adsorption/desorption tower 4. Finally, change-over valves 8-5 and 8-7 are installed in the circulating pipe L3 at locations upstream and downstream of the heating medium source 6, respectively, for the purpose of controlling a heating medium to be supplied to the adsorption/desorption tower 4.
The adsorption/desorption tower 4 is implemented in a double-drum or double-cylinder structure, wherein the inner drum or cylinder is filled with an adsorbent while the outer drum or cylinder is filled with a heat transfer medium. Parenthetically, silica gel is commonly used as the adsorbent with ethylene glycol or alcohols being used as the heat transfer medium. The circulating blower 3, the ozone generator 1 and the adsorption/desorption tower 4 are interconnected in this order by the circulating pipe L1 to thereby constitute an ozone gas circulation system.
Next, description will turn to operation of the conventional ozone storage system. Operation of the ozone storage system may globally be classified into two operation modes, i.e., an ozone adsorbing operation mode and an ozone desorbing operation mode.
Description will first be directed to the ozone adsorbing operation. In this operation mode, oxygen gas is supplied from the oxygen supplying source 2, whereby the ozone gas circulation system is maintained constantly at a predetermined pressure. In practical applications, this pressure is usually set at 1.5 kg/cm.sup.2. When oxygen gas is caused to flow through the ozone gas circulation system by means of the circulating blower 3 in the state in which the change-over valves 8-3 and 8-4 are opened, a part of the oxygen gas flow is transformed into ozone (i.e., ozonized) under the effect of silent electric discharge when the oxygen gas flows through an electric discharge gap defined between electrodes disposed within the ozone generator 1, whereby an ozonized oxygen gas is produced to be subsequently transported to the adsorption/desorption tower 4.
In this state, a refrigerating gas is supplied to the adsorption/desorption tower 4 from the coolant supply source 5 through the change-over valves 8-1 and 8-2 which are opened at this time point. As a consequence, the adsorbent charged in the adsorption/desorption tower 4 is cooled by the refrigerating gas to a temperature not higher than -30.degree. C. The adsorbent charged in the adsorption/desorption tower 4 adsorbs selectively ozone molecules from the ozonized oxygen gas, wherein residual oxygen gas is fed back to the circulating blower 3 through the pipe L1 by way of the change-over valve 8-3. An amount of oxygen consumed in the ozonization process is supplemented from the oxygen supplying source 2.
The amount of ozone molecules adsorbed by the adsorbent (hereinafter also referred to as the ozone adsorption quantity) remarkably vary in dependence on the temperature of the adsorbent. More specifically, the ozone adsorption quantity increases as the temperature of the adsorbent lowers, whereas the ozone adsorption quantity decreases as the temperature of the adsorbent rises. Accordingly, cooling of the adsorbent is effective for promoting the adsorption of ozone. On the other hand, the temperature of the adsorbent should be increased for the desorption of ozone from the adsorbent.
When the ozone adsorbent reaches a saturated ozone adsorption level, operation of the ozone storage system is changed over to the ozone desorbing operation mode. In this case, operations of the ozone generator 1, the circulating blower 3 and the coolant supply source 5 are stopped with the change-over valves 8-1, 8-2, 8-3 and 8-4 being closed. Subsequently, the heating medium source 6 and the water ejector 7 are put into operation with the change-over valves 8-5 and 8-7 being opened. When the change-over valves 8-5 and 8-7 are opened, a heating medium is fed to the adsorption/desorption tower 4 from the heating medium supply source 6. As a result of this, temperature of the adsorption/desorption tower 4 increases to thereby facilitate or promote desorption of the ozone molecules from the adsorbent.
When the change-over valve 8-6 is opened, ozone desorbed from the adsorbent filled in the adsorption/desorption tower 4 is drawn or drained into the water ejector 7 under the effect of depressurization to be thereby dispersed and solved in water. Thus, ozone can be fed to the ozone gas consumer in the form of ozone containing water. Due to the suction of ozone under depressurization, the pressure prevailing within the adsorption/desorption tower 4 will attain ca. 100 Torr. Upon completion of the desorption operation phase or mode, operation of the ozone storage system is changed over again to the ozone adsorption mode. In this manner, operation of the ozone storage system is performed repetitionally in a continuous manner.
With the structure of the conventional intermittent-operation type ozone supply system in which ozone is dispersed and solved in water in the desorption operation mode for supplying ozone to the ozone consumer in the form of ozone containing water, as described above, ozone will be extinct on the way to the ozone consumer because of short lifetime of ozone in water. Thus, the ozone supply system known heretofore suffers a problem that a continuous ozone supply to the ozone consumer at a predetermined rate is difficult or impossible. Furthermore, because ozone once dispersed and solved in water is extracted, utilization of ozone is essentially limited to water treatments because of short lifetime of ozone in water, giving rise to another inconvenience.
On the other hand, in the ozone adsorption operation mode, it is required to increase the partial pressure of ozone in the ozonized oxygen gas in order to realize adsorption of ozone by the adsorbent with a high efficiency. In that case, however, the ozone production efficiency of the ozone generating apparatus becomes lowered, involving a problem that storage of ozone with a desired efficiency is rendered difficult or impossible.